Web tensioning with adjustable counterweights for controling the spacing of imprints

ABSTRACT

A sheet-handling apparatus in which a sheet is moved past a printing assembly and which has independent first and second variable force sheet tensioning devices disposed upstream and downstream, respectively, of the printing assembly. The forces exerted by the tensioning devices are varied as determined by control means to increase or decrease the speed with which the sheet moves past the printing assembly and thereby control the relative position of imprints from the assembly on the sheet.

United States Patent Donald C. Anderson Lafayette;

Momir Kodich, El Cerrito, Calif. 871,709

Nov. 20, 1969 Feb. 16, 1971 Hexcel Products, Inc.

Berkeley, Calif.

Continuation of application Ser. No. 587,716, Oct. 19, 1966, now abandoned.

inventors Appl. No. Filed Patented Assignee WEB TENSIONING WITH ADJUSTABLE COUNTERWEIGHTS FOR CONTROLLING THE SPACING 0F IMPRINTS 3 Claims, 1 Drawing Fig.

U.S. Cl 101/225, 101/426; 226/2; 242/75; 226/195 Int. Cl B41f 13/02 Field of Search 101 /2 l 9- 228, 178-182, (Web Tensioning Digest), 426; 226/27-29, 2, 195; 242/75, 75-2 5.6] References Cited UNITED STATES PATENTS 1,653,199 12/1927 Belcher 101/228x 1,855,525 4/1932 MacArthur.... l0l/l81X 2,067,755 l/l937 Dyer, Jr 226/24X 2,453,982 11/1948 Huck 101/181 2,497,909 2/1950 Poole lOl/l 8] 2,962,962 12/1960 Smith l0l/248X 3,233,539 2/1966 Cahn;.. 101/181 3,280,737 10/1966 Huck l0 l/225X Primary Examiner-Robert E. Pulfrey Assistant Examiner-4. Reed Fisher Attorney-Townsend and Townsend ABSTRACT: A sheet-handling apparatus in which a sheet is moved past a printing assembly and which has independent first and second variable force sheet tensioning devices disposed upstream and downstream, respectively, of the printing assembly. The forces exerted by the tensioning devices are varied as determined by control means to increase or decrease the speed with which the sheet moves past the printing assembly and thereby control the relative position of imprints from the assembly on the sheet.

PATENTED FEB 1 6 I9?! INVENTORS DONALD c. ANDERSON BY MOMIR KODICH MUM ATTORNEYS WEB TENSIONING WITH ADJUSTABLE COUNTERWEIGHTS FOR CONTROLLING THE SPACING F IMPRINTS This is a continuation of Ser. No. 587,716, filed Oct. 19, 1966 now abandoned.

This invention relates to improvements in sheet-handling apparatus and, more particularly, to apparatus and a method for accurately controlling the spacing of transverse printed lines on a movable web.

The present invention resides in apparatus and a method for applying controllable tension forces to a movable sheet or web to which transverse printed lines are applied as the web moves through a printing station. The purpose of controlling the tension is to permit minute changes to be made in the speed of web relative to the printing structure. These speed changes have a direct effect on the precise spacing of lines on the web. Thus, to increase the line spacing, the web speed is increased,

with respect to the printing roll surface speed and to decrease the line spacing, the web speed is decreased. The speed changes result from changing the tension in the web upstream or downstream of the printing station. Extremely fine control in the line spacing can be attained since the change in the tension force on the web can, in practice, occur in relatively small increments.

The concepts of this invention are especially adapted for use in the manufacture of honeycomb core structures by an expansion process wherein a number of sheets provided with transverse glue lines thereon are stacked so that adjacent sheets become connected together at the glue lines. It is extremely important that the glue lines of alternate sheets be accurately located to assure that the honeycomb configuration results when the stack of sheets is expanded. Otherwise the cells of the honeycomb core will be irregular in size and shape and the core itself will not be homogenous throughout. The glue line spacing is the critical parameter assuming the sheets are properly cut and stacked, since this spacing must not vary from sheet to sheet to any appreciable extent.

The present invention assures that the glue line spacing will be within a predetermined range by controlling the speed of the web through the printing station. The spacing of the lines can be monitored to determine if the lines are to be properly applied to the web so that corrections can immediately be made, if necessary, by varying the tension of the web. The web, after it has been printed, may then be cut into sheets for stacking in the manner described or may be wound on a roll for subsequent use.

Required variations in the line spacing will generally be extremely small for any given cell size, usually in the order of no more than about 0.010 to 0.020 inch per -foot linear web length. Provision must therefore be made for relatively small changes in the speed of the web. The present invention allows for this by providing structure for applying constant tension forces to the web upstream and downstream of the printing rolls while permitting the tension forces to be varied. The resulting tension balance or inbalance on the upstream and downstream sides of the printing rolls thus effects either an increase or a decrease in web speed. A preferred form of the structure for applying web tension is a rockable dancer arm having an adjustable counterweight thereon. A dancer roll mounted on the dancer arm applies a force of a magnitude which is determined by the setting of the counterweight to one face of the web. Relative large changes in counterweight operating position and the resulting changes in the web tensioning influence the web speed past the printing rolls in only minute increments. Thus the invention provides a simple, stepless, micro-control and ad justability of the web speed past the printing rolls and economical means for adjusting the print line spacing.

Furthermore, the present invention isolates the web portion passing the printing rolls from the upstream web payout drum and the downstream web takeup drum with capstan drive means positioned between the printing rolls and the payout and takeup rolls. Variations in the web tensioning between the capstan drive means and the payout and takeup rolls are thereby prevented from causing an unintentional change in the tensioning balance or inbalance of the web portion disposed on the upstream and downstream sides of the printing rolls. Such a change in the web tensioning would alter the print line spacing for the above-described reasons.

The primary object of this invention is to provide a sheet printing apparatus and method wherein a movable sheet is subjected to variable tension forces as it passes through a printing station or nip so that minute changes in the speed of the sheet relative to the theoretical speed of the printer nip can be made by varying the tension forces on the sheet to thereby permit minute changes in the pattern with which the sheet is printed at said station. A

Another object of this invention is to provide apparatus of the type described wherein spaced, transverse lines are printed on thesheet as it moves through the printing station and the speed of the sheet relative to the printing station can be varied by changing the tension of the web on one side of the station, whereby the rate at which the lines are applied to the sheet and thereby the line spacing can be made a function of the sheet speed and thereby the sheet tension.

Other objects of the invention will become apparent as the following specification progresses, reference being had to the accompanying drawing.

The drawing shows a schematic representation of the apparatus of the invention through which an elongated, flexible sheet or web 10 passes. One end 12 of the web is shown as it enters drive means 14. The source of web 10 may, for example, be a roll adjacent to drive means 114.

After leaving drive means 14, web 10 passes beneath a dancer roll 16, about a pair of idler rolls l8 and 20 and then into and through a printing station 22. The web passes out of the printing station into and through a drying station 24, out of the drying station and about idler rolls 26, 28 and 30, and then about a second dancer roll 32. The web then passes about an idler roll 34 and into and through second web drive means 36 from whence it passes over an idler roll 38 and then to a point of use or to another roll on which it is wound.

As the web passes through printing station 22, it is printed with transverse lines 40 and 42 on opposed sides thereof. The printed lines are dried in chamber 24 before the web emerges and passes to the downstream rolls and drive means. Dancer rolls 16 and 32 maintain tension on the excess web length or loops between drive means 14, 36 and printing station 22, on the upstream and downstream portions of the web as it is being printed. These tension forces are independent of the moving forces applied to the web by drive means 14 and drive means 36. Thus, these tension forces act on the printer nip rolls 44 and 46 and determine the speed of the web through printing station 22 inasmuch as the upstream and downstream tensions are unequal in magnitude and thereby provide a resultant unbalanced force on the web.

The printing structure at station 22, for purposes of illustration, includes a pair of printing zones defined by opposed nip rolls 44 and 46. As shown in the drawing, one set of rolls is disposed above the other set but this arrangement can be changed if desired. Rolls 46 provide the means by which the lines 40 and 42 are applied to the moving web whereas rolls 44 provide backing support for respective rolls 46. Rolls 44 and 46 are rotated under the influence of a power source which is independent of drive means 14 and drive means 36. Thus, the

, speed of the web through printing station 22 can be minutely increased or decreased with respect to the surface speeds of rolls 44 and 46, without interaction with drive means 14 and 36.

Drive means 14 includes a drive roll 48 forming a part of an S-drive unit whereby the web is partially wound about roll48 and is held in frictional engagement therewith. Similarly, drive means 36 has a drive roll 50 forming a part of an S-d'rive unit for the same purpose. A

Each of the dancer rolls l6 and 32 are mounted'o'n one end of a dancer arm pivotally mounted for rotationabout a horizontal axis. Arm 52 on which roll 1.6 is mounted is'ro tatable about an axis 54 and has an adjustable counterweight 56 at its opposite end. Arm 58 to which dancer roll 32 is connected is pivoted on an axis 60 and also has an adjustable counterweight 62 on its opposite end. The dancer arms are mounted for free pivotal movement on suitable supports so that dancer rolls l6 and 32 rest on and are supported by the upper face of web 10.

In operation, the tension forces on the web upstream and downstream of station 22 are initially established by adjusting the operative positions of counterweights 56 and 62 along respective arms 52 and 58. Thus, the weights of dancer rolls 16 and 32 as partially counteracted by counterweights 56 and 62 will be the sources of the upstream and downstream tension forces, respectively.

Drive means 14 and drive means 36 are placed in operation and simultaneously with this action, rolls 44 and 46 of printing station 22 will be caused to rotate in the proper directions to effect printing of lines 40 and 42 on the web as it moves toward the drying station.

For given upstream and downstream tension forces and given conditions of speed, impression pressure, wet thickness, etc. at rolls 44 and 46, the spacing between adjacent lines on either face of the web will be a predetermined value. This spacing can be monitored at a convenient location downstream of printing station 22. If the spacing departs from the desired value, it can be changed by varying either or both of the upstream and downstream tension forces.

For instance, if it is desired to increase the spacing, the downstream tension can be increased by moving counterweight 62 closer to axis 60. This action increases the effective weight of dancer roll 32 as applied to the moving web. The spacing can also be increased by decreasing the upstream tension force on the web by moving counterweight 56 in a direction away from axis 54. Also, the tension increase can be a combination of these two steps.

To decrease thespacing the downstream tension force can be decreased or the upstream tension force can be increased or the change can result from a combination of both of these steps. For either a net increase or a net decrease in the tension forces, there will always be a change in the operating speed of the web through the printing station and this speed change is always relative to the linear speeds of rolls 44 and 46. Thus, the line spacing on the web is a direct function of the upstream and downstream tension forces on the web.

The advantage of using both upstream and downstream tension applied by rolls l6 and 32 is that increased sensitivity is achieved for web thicknesses of substantially any workable gauge. This is important since significant changes in line spacing are extremely small in many types of applications such as in the manufacture of honeycomb core structures. These small spacing changes can be of the order of .01 percent which could, for example, correspond to a change of .005 inch in 50 inches. It is clear, therefore, that this invention provides the sensitivity needed to maintain the web spacing at a desired value.

Means for applying tension to the web other than that described herein can be used if desired. Thus, the invention is downstream sides of the printing rolls are thus avoided. in this manner, the web speed and the printing roll surface speed can be equalized, or varied if required, to control and maintain an exact spacing of the print lines on the web without discernible tolerances.

While one embodiment of this invention has been shown and described, it will be apparent that other adaptations and modifications can be made without departing from the true spirit and scope of the invention.

We claim:

1. Sheet-handling apparatus comprising: a support; a printing assembly on said support including a pair of rotatable rolls in proximity to each other and disposed for receiving therebetween a flexible sheet movable along a path of travel transverse to said rolls, whereby the sheet is printed as it moves between the rolls; a first dancer arm on said support upstream of said printing assembly with respect to said path, said first dancer arm being disposed for engaging the sheet to apply a first tension force thereto acting in the upstream direction thereof; a second dancer arm on said support downstream of said printing assembly and disposed for engaging the sheet to apply a second tension force thereto acting in the downstream direction thereof, each of said dancer arms being mounted intermediate its ends for free pivotal movement about a-horizontal axis and having a sheet-engaging roller at one of its ends and an adjustable counterweight at its opposite end; first sheet drive means upstream of said first dancer arm for moving the sheet in the downstream direction; and second sheet drive means downstream of said second dancer arm for moving the sheet in said downstream direction.

2. Sheet-handling apparatus comprising: a sheet printing assembly adapted to be disposed in the path of travel of a movable sheet; means upstream of said assembly and engageable with said sheet on said path for applying a first tension force to the sheet; means downstream of said assembly and engageable with said sheet for applying a second tension force to the sheet; each of said upstream means and said downstream means including an arm mounted intermediate its ends for free pivotal movement about a horizontal axis, roller means on one end of the arm for engaging the sheet, and an independently adjustable counterweight on the opposite end of the arm, whereby the difference between the weight of said roller means and the counterweight will define a force exerted on the sheet to provide the respective tension force; and drive means independent of said upstream means and of said downstream means for moving said sheet in one direction along said path.

3. In a method for substantially instantaneously adjusting the speed of a sheet passing a sheet-handling station to maintain the spacing between adjacent transverse print lines imprinted on the sheet at said station constant over the length of the sheet, the method including the steps of feeding the sheet towards the sheet-handling station; passing the sheet through the sheet-handling station; withdrawing the sheet from the handling station; printing spaced lines on said sheet as it moves through said station, the lines being spaced in a direction transverse to the movement of the sheet; and adjusting the tension applied to the sheet at the upstream and downstream positions of the station, the adjustment of the tension being performed by means upstream of said station and engageable with the sheet for applying a first tension force to the sheet and by means downstream of said station and engageable with said sheet for applying a second tension force to the sheet, each of said upstream means and said downstream means including an arm mounted intermediate its ends for free pivotal movement about a horizontal axis, roller means on one end of the arm for engaging the sheet, and an indepen-, dently adjustable counterweight on the opposite end of the arm, whereby the difference between the weight of said roller means and the counterweight will define a force exerted on the sheet to provide the respective tension force, the improvement comprising the steps of: applying a first tension force downstream of the station to the sheet with the downstream roller engaging means; applying a second tension force upstream of the station to the sheet with the upstream roller engaging means; monitoring the spacing between said lines printed onto the sheet; adjusting the weight on at least one of the counterweights to thus vary at least one of said tension forces in response to changes in the spacing of said lines to change the speed of the sheet moving past said station and 'thereby maintain said constant spacing between said lines; and

maintaining the varied effective force constant until a change in said constant spacing between said print lines is again monitored. 

1. Sheet-handling apparatus comprising: a support; a printing assembly on said support including a pair of rotatable rolls in proximity to each other and disposed for receiving therebetween a flexible sheet movable along a path of travel transverse to said rolls, whereby the sheet is printed as it moves between the rolls; a first dancer arm on said support upstream of said printing assembly with respect to said path, said first dancer arm being disposed for engaging the sheet to apply a first tension force thereto acting in the upstream direction thereof; a second dancer arm on said support downstream of said printing assembly and disposed for engaging the sheet to apply a second tension force thereto acting in the downstream direction thereof, each of said dancer arms being mounted intermediate its ends for free pivotal movement about a horizontal axis and having a sheetengaging roller at one of its ends and an adjustable counterweight at its opposite end; first sheet drive means upstream of said first dancer arm for moving the sheet in the downstream direction; and second sheet drive means downstream of said second dancer arm for moving the sheet in said downstream direction.
 2. Sheet-handling apparatus comprising: a sheet printing assembly adapted to be disposed in the path of travel of a movable sheet; means upstream of said assembly and engageable with said sheet on said path for applying a first tension force to the sheet; means downstream of said assembly and engageable with said sheet for applying a second tension force to the sheet; each of said upstream means and said downstream means including an arm mounted intermediate its ends for free pivotal movement about a horizontal axis, roller means on one end of the arm for engaging the sheet, and an independently adjustable counterweight on the opposite end of the arm, whereby the difference between the weight of said roller means and the counterweight will define a force exerted on the sheet to provide the respective teNsion force; and drive means independent of said upstream means and of said downstream means for moving said sheet in one direction along said path.
 3. In a method for substantially instantaneously adjusting the speed of a sheet passing a sheet-handling station to maintain the spacing between adjacent transverse print lines imprinted on the sheet at said station constant over the length of the sheet, the method including the steps of feeding the sheet towards the sheet-handling station; passing the sheet through the sheet-handling station; withdrawing the sheet from the handling station; printing spaced lines on said sheet as it moves through said station, the lines being spaced in a direction transverse to the movement of the sheet; and adjusting the tension applied to the sheet at the upstream and downstream positions of the station, the adjustment of the tension being performed by means upstream of said station and engageable with the sheet for applying a first tension force to the sheet and by means downstream of said station and engageable with said sheet for applying a second tension force to the sheet, each of said upstream means and said downstream means including an arm mounted intermediate its ends for free pivotal movement about a horizontal axis, roller means on one end of the arm for engaging the sheet, and an independently adjustable counterweight on the opposite end of the arm, whereby the difference between the weight of said roller means and the counterweight will define a force exerted on the sheet to provide the respective tension force, the improvement comprising the steps of: applying a first tension force downstream of the station to the sheet with the downstream roller engaging means; applying a second tension force upstream of the station to the sheet with the upstream roller engaging means; monitoring the spacing between said lines printed onto the sheet; adjusting the weight on at least one of the counterweights to thus vary at least one of said tension forces in response to changes in the spacing of said lines to change the speed of the sheet moving past said station and thereby maintain said constant spacing between said lines; and maintaining the varied effective force constant until a change in said constant spacing between said print lines is again monitored. 